Vehicle engines widely adopt cylinder heads and cylinder blocks made of aluminum alloy for the purpose of reducing the weight and providing cooling performance. The cylinder head has a complicated structure internally including intake ports for mounting intake valves, exhaust ports for mounting exhaust valves, spark plug holes for mounting spark plugs, part of combustion chambers for exploding fuel, a water jacket for allowing cooling water to circulate, and others. The cylinder head is usually produced by casting using a number of sand cores to integrally form the intake ports, the exhaust ports, the water jacket, and others. Accordingly, the cylinder head is formed with sand removing holes to remove the sand cores by crushing or shattering them after the cylinder head is taken out of a casting mold. The cylinder head from which the cores have been removed is then subjected to machining, for example, to form bolt holes by a drill or the like or grind the surface of each port. If foreign matters such as sand of the cores and chippings or cuttings resulting from the machining stay in the cylinder head, product quality in an engine may be deteriorated. Therefore, the processed cylinder head is heretofore subjected to cleaning for removing the foreign matters.
For instance, Patent Literature 1 discloses a technique for cleaning a cylinder head by rotating the cylinder head grasped with a clamp, ejecting cleaning liquid through cleaning nozzles arranged around the cylinder head toward the cylinder head. A cylinder head cleaning method and a cylinder head cleaning device in Patent Literature 1 are configured to move the cleaning nozzles toward or away from the cylinder head to maintain a fixed distance between the nozzles and the cylinder head. Accordingly, the cleaning liquid ejected from each nozzle effectively acts on all surfaces of the cylinder head to be cleaned, thus achieving better cleaning effects.
However, the cylinder head cleaning method disclosed in Patent Literature 1 is conducted by ejecting the cleaning liquid from outside of the rotating cylinder head. Thus, the cleaning liquid entering in the water jacket flows slowly at a flow velocity of 0.5 m/s and in a small flow amount and therefore could not produce a flow in the water jacket. A cleaned cylinder head is normally subjected to visual checks by a person for checking whether or not foreign matters remain in the cylinder head through a microscope or the like. If foreign matters are found, they are removed one by one by hand. Regarding the cylinder head cleaned by the cylinder head cleaning method of Patent Literature 1, about 80% of foreign matters found in one cylinder head would be found in the water jacket. Therefore, the cylinder head cleaning method and the cylinder head cleaning device of Patent Literature 1 could not sufficiently clean the water jacket.
On the other hand, Patent Literatures 2 and 3 propose techniques of cleaning the inside of a water jacket in which foreign matters are apt to remain.
The cylinder head cleaning method and cylinder head cleaning device of Patent Literature 2 are configured such that, as first to third cleaning steps shown in FIGS. 24A to 24C, while compressed air is supplied to holes 103c, 103d, and 103e communicating with recesses 102a, 102b, and 102c of a water jacket 102 formed in a cylinder head 101, cleaning nozzles 104, 105, and 106 are selectively sequentially brought into contact with holes 103a, 103b, and 103f communicating with the water jacket 102, thereby ejecting cleaning liquid W from the cleaning nozzles 104, 105, and 106. Accordingly, different flows are created near the recesses 102a, 102b, and 102c of the water jacket 102, thereby discharging and removing the foreign matters remaining in the recesses 102a, 102b, and 102c together with the cleaning liquid W to the outside of the cylinder head 101.
The cylinder head cleaning method and the cylinder head cleaning device of Patent Literature 3 are configured such that as shown in FIG. 25 a moving means 209 brings a plurality of nozzles 204, 205, 206, 207, and 208 provided in a cleaning bath 201 and a seal pad 213 into close contact with hole parts 210b to 210g selected from a plurality of hole parts 210b to 210j formed in a cylinder head 210. In a cleaning liquid process device 202, cleaning liquid W filtered through a filter 212 is fed to each of the nozzles 204 to 208 from a cleaning liquid supply pump 203 and ejected into the hole part 210b to 210g at high pressure. The cleaning liquid W forms flows while causing turbulent flows in a water jacket 210a, thereby cleaning the inside of the water jacket 210a. Foreign matters remaining in the water jacket 210a are sucked in the flows of the cleaning liquid W and thus discharged together with the cleaning liquid W through the hole parts 210h, 210i, and 210j into the cleaning bath 201.